Thermally tunable electron discharge device



Oct. 26, 1948. P. SPENCER THERMALLY TUNABLE ELECTRON DISCHARGE DEVICE 2 Sheets-Sheet 1 Filed May 24, 1944 Oct. 26, 1948. P. 1... SPENCER 2,452,073

THERMALLY TUNABLE ELECTRON DISCHARGE DEVICE Filed May 24, 11944 2 Sheets-Sheet 2 firm r0 PL'AC) A. SPA-AMER,

W ZTZ Patented Oct. 26, 1948 THERMALLY .TUNABIJE ELECTRON DISCHARGE "DEVICE Percy L. Spencer,jW'es't Newton, Mass, assignor to Raytheon .Manufacturing Company, Newton,

Mass a corporation of Delaware Application 'May'24, 1944,Serial No. 537119 The present invention charge devicespsuch as magnetrons, for example, and more particularly to those in which'the frequency of the oscillations produced is determinedby the dimensions of the internal structure.

In devices of the above-mentioned type, variations in temperature tend to cause variations in the dimensions of the internal structure of the device that are sufficient to produce such large variationsin frequency that'frequencies of oscillations produced by the device are outside the permissible frequency tolerances. This may prove objectionable, particularly in beacon operation, where the device must be held within close frequency tolerances under all-conditions.

An object of the present invention is to provide an electron discharge device of the aforesaid type'which comprises simple, reliable means for keeping the frequencies within permissible frequency tolerances under varying temperature conditions.

Another object of the invention is to provide a novel'frequency stabilizing means for devices of the aforesaid type,

The aforesaid objects and such other aims and objects of the invention as may hereinafter appear will be best understood from the following description, taken inconnection with the accompanying drawings of one embodiment of the invention herein iven for illustrative purposes.

In the drawings:

Fig. 1 isa vertical section through a magnetron embodying an illustrative embodiment of the invention;

Fig. 2 is a cross-section taken on line 2-2 of Fig.

Fig. 3 is a side elevation, on an enlarged scale and partly in section, of the frequency stabilizing means shown in Fig. 1; v

Fig. 4 is a top plan view of the parts shown in Fig. 3; and

Fig.5 is a perspective view of the mounting of the frequency stabilizing means. 7

Referring to the drawings, the illustrative embodiment of the invention therein shown comprises a cylindrical envelope 2 including caps 4 and B by which it is closed at both ends and which are hermetically sealed in place. Said envelope 2 and caps 4 and 6 may be made of copper or other suitable conductive material and said envelope has formed upon its inner surface a central, annular projection 8 to which are soldered aplurality of radially disposed plates llLsuitably spaced from one another. Said :plates :may be .3Claims. (omit- 9 relates to electron'dis- I be insulated .from'said sleeve.

,2 stamped out of'a-sheet of highly conductive copper and rtheirinner ends form anode faces which cooperate with a cathode I2, supported substantially centrally of said anode faces. The cathode 12 will preferably be of :the indirectly heated, oxide-coated, thermionic type, provided 'with an outer conducting sleeve l4, coatedwith electronemissive oxides, and aninternal heater of which the end conductors I18 and 2 project from the opposite ends of the cathode structure. One of the said conductors, the conductor 20 for eXample, may be electrically connected to said outer cathodesleeve 84, while the other conductor will Light, conducting shields 22, :24 maybe mountediadj-acentthe two ends otcathode'lt, toprevent electron beams from being projected outwardly toward the end caps 4: and "6. The cathode l2 will preferably be supportedby a'cathode and heater lead-inconductor 26 welded to the .end of conductor 20, which, as previously "stated, is electrically connected to said cathode and to one end of the cathode heater. iSaid lead-in conductor '26 is sealed .through'a glass seal 28 mounted at the 'iouter-"endof a conducting pipetfi which extends through the wall LOf envelope 2 and is hermetically secured itherein adjacent the lower end thereof. A second lead-in-conductor 32 is sealed through asimilar glass seal .34 mounted at the outer end of :a conducting pipe 38 also hermeticallyrsealed through the wall of envelope 2 at the upper end thereof. The inner end of said leadin conductor 32 may be'welded to'the free 'end of conductor l8.

When such an electron discharge device is placed between suitable magnetic poles 38and 4D to create-a longitudinal magnetic field, and 'the deviceis energized, oscillations will "be generated which may beledfout of the device by a coupling loop 42 extending into the space between "two of said plates ill. One'end .ofisaid coupling loop 42 is connected to .theinner end of a conducting pipe 44,;hermetioal1ysealed through the wall of of simplicity the .pipe 44 'is'shownasbroken away atrits central portion, but it will be understood that said pipe may be substantially of the same length as :pipes 30. and 36.

An additional conducting pipe, not shown, may-be electrically connected 'toisaid pipe 44 and form with said con- :"ductor -46 :a concentric line through which the high frequency oscillations generated by the device may be conducted to a suitable utilization circuit.

Each pair of anode arms or plates l forms with the portion of the projection 8 between them an oscillating cavity II. A capacitance exists between the cathode I 2 and the end faces of said anode arms i0 and also between the side walls of each oscillating cavity. The conductive path around each cavity, afforded by the side walls thereof, constitutes an inductance. The anode, therefore, is so designed and spaced relatively to the cathode that said inductances and capacitances constitute tuned circuits. It is desired that the circuits shall be resonant at definite, predetermined frequencies at which the device is to be operated. The device isintended to operate so that eachoscillating cavity H shall be tuned to the frequency at which each of the other oscillating cavities i l oscillates.

As previously sta ted, one of the objects of the present invention is to provide an electron discharge device of the general type referred to comprising simple and reliable meansfor keeping the frequency of oscillationsgenerated by the device within permissible frequency tolerances, irrespective of variations in temperature. This object is realized in accordance with thepresent invention by the provision of novel frequency stabilizing means.

In the illustrative embodiment of the invention herein disclosed, the means employed comprises a relatively thin member 5!], preferably of annular shape and positioned with the annular or ring portion 52 thereof adjacent said anode arms Ill and the circular aperture 53 over one end of said cathode l2. The end conductor l8 of the cathode projects through said aperture and is welded to the lead-in conductor 32, as previously described. Said annular member is i joined at one side to one end of a thermostatic device which conveniently may consist of a bimetallic strip, herein comprising the, two metal laminae 54 and 56 (see Figs. 3 and 5), the other end of which is joined to a suitable fixed part of the device. Herein said lead-in conductor 32 is conveniently utilized for this purpose, saidbimetallic strip being firmly connected to said conductor 32 by ashort support 5| welded to said conductor and to said bimetallic strip. (See Fig. 5.) Said bimetallic strip is so designed that the lamina 54 has the lower coeficient of expansion and thelamina 56 the higher one,

A rise in temperature will expand the anode structure and its oscillating cavities and thus tend to decrease the frequency of the oscillations generated by the device; but as the lamina 56 has the higher coeflicient of expansion, this same increase in temperature will tend to curve the end 58 of said bimetallic strip toward said conduotor 32, thus moving the annular member 50 away from the anode structure and thereby tendin to increase the frequency. A decrease in temperature on the other hand will tend to contract the anode structure and its oscillating cavities and thus increase the frequency; but a decrease in temperature will tend to curve the bimetallic strip away from said conductor 32, thus moving said annular portion 52 toward said anode structure, thereby to increase the frequency. These relative adjustments of the anode structure and the tuning member 50 will thus substantially compensate each other.

, The device having been assembled with the annular portion 52 of the tuning member 50 in "thereof to the same degree.

such a position in respect to the anode arms In that at a given temperature the frequency of the oscillations generated by the device is at a predetermined value within the permissible frequency tolerances, the frequency at which the device oscillates will therefore be kept automatically within such frequency tolerances by the above described novel frequency stabilizing means, irrespective of temperature variations.

In accordance with my present understanding of the operation of the invention, varying the position of said annular tuning member 50 will vary the capacitance of the anode structure, as above described, without affecting the inductance Therefore, varying said capacitance will tune the frequency of the magnetron in the desired manner.

The present invention comprises a minimum of parts and any danger of its getting out of order is negligible. It is also extremely simple in constructi-on and the tuning member is of light weight and its operation is independent of and therefore unhampered by the movement of other parts possessing more or less inertia. All this contributes to making the frequency stabilizing device embodying the present invention remarkably sensitive to changes in temperature and very reliable in operation. Other advantages will suggest themselves to those skilled in the art.v v

Wherever the expression a plurality is used it is to be understood as meaning two or more.

I am aware that the present invention can be embodied in other specific forms without departing from the spirit or essential attributes thereof, and I therefore desire the present description to be considered in all respects as illustrativeand not restrictive, reference being had to the appended claims rather than to the aforesaid description to indicate the scope of the invention.

What is claimed is: I

1. An electron discharge device comprising: an envelope containing a cathode; an anode structure including a plurality of electron-receiving portions adjacent said cathode, and a plurality of cavities between said portions; said anode structure providing inductance and capacitance; and frequency stabilizing means including a tuning member, and a thermostatic, bimetallic strip fixed at one end to said device; said bimetallic strip including two laminae having different coefficients of expansion; said strip at its other end supporting said tuning member, with the lamina of said strip having-the greater coefiicient of expansion adjacent said electronreceiving portions; said strip being operatively connected to said tuning member for adjusting the position of said tuning member relatively to said electron-receiving portions, and being responsive to variations in temperature to vary said capacitance, and, thereby the frequency of the oscillations generated by said device.

2. An electron discharge device comprising: an envelope containing a cathode; an anode structure including a plurality of electron-receiving portions adjacent said cathode, and a cavity between said portions; said anode structure providing inductance and capacitance; and frequency stabilizing means including atuning member, and a thermostatic, bimetallic strip fixed at one end to said device; said bimetallic strip including two laminae having different coeificients of expansion; said strip at its other end supporting said tuning member, with the lamina of said strip having the greater coeflicient of expansion adjacent said electron-receiving por- O tions; said strip being operatively connected to said tuning member for adjusting the position of said tuning member relatively to said electron-receiving portions, and being responsive to variations in temperature to vary said capacitance, and thereby, the frequency of the oscillations generated by said device.

3. A magnetron comprising: an envelope containing a cathode; an anode structure adjacent said cathode and having inductance and capacitance; and frequency stabilizing means including a tuning member, and a thermostatic, bimetallic strip fixed at one end to said device; said bimetallic strip including two laminae having different coefficients of expansion; said strip at its other end supporting said tuning member, with the lamina of said strip having the greater coefficient of expansion adjacent said anode structure; said strip being operatively connected to said tuning member for adjusting the position of the latter relatively to said anode structure, and being responsive to variations in temperature to vary said capacitance, and thereby, the frequency of the oscillations generated by said magnetron.

PERCY L. SPENCER.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 1,884,591 Davis Oct. 25, 1932 2,114,846 Little Apr. 19, 1938 10 2,183,215 Dow Dec. 12, 1939 2,251,085 Unk July 29, 1941 2,374,810 Fremlin May 1, 1945 2,404,212 Bondley July 16, 1946 2,408,903 Biggs et a1. Oct. 8, 1946 2,413,364 McCarthy Dec. 31, 1946 2,418,844 Le Van Apr. 15, 1947 2,422,465 Bondley June 17, 1947 FOREIGN PATENTS Number Country Date 422,869 Great Britain Jan. 21, 1935 537,518 Great Britain Jan. 25, 1941 

